Sweat analysis using indirect ion-selective electrode on the routine chemistry analyser meets UK guidelines

Abstract

Background According to consensus documents, sweat testing remains the standard for diagnosing cystic fibrosis. We studied a novel method of sweat analysis on two chemistry platforms: Dimension Vista (Siemens Healthcare Diagnostics) and Aeroset (Abbott). Methods Sweat collected from healthy individuals and aqueous samples in the critical range for sweat analysis were measured using the Orion 290 plus (Thermo Electron Corporation), Chiron 925 chloride analyser (Sherwood Scientific Ltd), flame photometry, sweat-chek analyser and indirect ion-selective electrodes (ISE) of Vista and Aeroset. For measurement on ISE, an addition protocol was designed. Results Within-run and between-run variation coefficients of Aeroset and Vista remained <5% as prescribed by UK guidelines. The correlation between the chloride analyser and chloride concentrations analysed on Vista or Aeroset was, respectively, y = 0.96x + 7.61 ( r2 0.990) and y = 0.97x + 1.10 ( r2 0.930) and between sweat-chek (conductivity) and sodium concentrations analysed on Vista or Aeroset was, respectively, y = 1.08x - 4.0 ( r2 0.967) and y = 1.13x - 1.00 ( r2 0.939). When classified according to medical decision rules (30 mmol/L and 60 mmol/L chloride, combined with sodium concentration), the same classification was found with the ISE-module and conventional methods for all samples. Conclusion We describe a simple procedure for sweat analysis using the ISE-module of two different chemistry platforms. This procedure meets the requirements as described in UK guidelines.